A utility class to build Javascript from CoffeeScript. Builds single file, a folder, or a tree. Optional rebuild supports lazy building in production. Specify a lib directory.

coffee_to_js_builder.rb

require 'coffee-rails'
require 'fileutils'

class JsBuilder

  def initialize(base_directory:, bin_folder: 'bin', lib_directory: File.join(base_directory, 'lib'), rebuild: false)
    @base_directory = base_directory
    @lib_directory = lib_directory
    @bin_folder = bin_folder
    @rebuild = rebuild
  end

  def build(relative_path:, deep: true)
    path = ensure_path relative_path
    filepaths = if File.directory? path
      Dir["#{path}/#{'**/' if deep}*.coffee"]
    else
      [path]
    end
    js_filepaths = filepaths.each(&method(:compile))
    lib_filepaths = Dir["#{@lib_directory}/**/*.coffee"]
    lib_js_filepaths = lib_filepaths.each(&method(:compile))
    [js_filepaths, lib_js_filepaths]
  end

  def clean(relative_path:, deep: true)
    path = ensure_path relative_path
    directories = Dir.glob "#{path}/#{'**/' if deep}"
    directories.each do |directory|
      bin_directory = File.join directory, @bin_folder
      FileUtils.rm_rf bin_directory
    end
  end

private

  def compile(filepath)
    directory = File.dirname filepath
    filename = File.basename filepath, '.coffee'
    if @rebuild
      bin_directory = File.join directory, @bin_folder
      FileUtils.rm_rf bin_directory
    end
    js_path = "#{File.join bin_directory, filename}.js"
    return js_path if File.exists?(js_path)
    file = File.open filepath
    js = CoffeeScript.compile file
    create_file js_path, js
    js_path
  end

  def create_file(path, content)
    dirname = File.dirname path
    FileUtils.mkdir_p dirname unless File.directory? dirname
    File.open(path, 'w') { |f| f.write content }
  end

  def ensure_path(relative_path)
    path = File.join @base_directory, relative_path
    raise "Cannot process javascript; path not found: #{path}" unless File.exist? path
    path
  end

end